Automatic switch as used in telephone systems



1 Nov. 10, 1 942. E. E. COMFORT 2,301,773

AUTOMATIC SWITCH AS USED IN TELEPHONE SYSTEMS Filed Nov. 9, 1940 INVENTOR EDGAR EUGENE COMFORT ATTORNEY Patented Nov. 10, 1942 AUTOMATIC SWITCH AS USED IN TELEPHONE SYSTEMS Edgar Eugene Comfort, Liverpool, England, as-

signor to Associated Telephone & Telegraph Company, Chicago, 111., a corporation of Delaware Application November 9, 1940, Serial No. 365,001 In Great Britain December 27, 1939 2 Claims.

The present invention relates to automatic switches of the two-directional type with longitudinal and rotary motion as used in telephone or like systems, and is more particularly concerned with auxiliary contact banks and wipers such as the so-called vertical banks and wipers which are provided where switches of the vertical and rotary type are required to perform a vertical hunting operation as in the case of line finder switches.

One type of vertical marking bank which has found considerable employment is mounted on the righthand side of the switch and has twentytwo contacts arranged in two rows of eleven contacts each separated by a thin layer of insulation, the contacts being engaged by vertical wipers comprising two springy blades insulated from one another. Accordingly it will be appreciated that only one set of bank contacts and the relevant engaging wiper blade will be readily visible for adjustment purposes.

In order to ensure that a switch so equipped can be removed from its mounting rack without any special releasing operations having to be performed in respect of the vertical wiper and bank, it has been arranged for the vertical bank to be pivotally mounted for instance in the manner described in British specification No. 467,031. This construction enables the vertical bank to swivel into or out of position as required, and in order to allow of the necessary movement the wiring to the contacts thereof must be arranged in a cable form. In certain circumstances however this cab-1e form may be so bulky that it interferes with the swivelling movements of the vertical bank and tends to prevent it retaining its operative position and it may also introduce difiiculties in connection with the removal of the adjacent switches from the mounting rack. A further point which requires care when a switch is being replaced on the mounting rack is to notice that the vertical wiper blades have not swung inwards so that they point towards the ordinary contact banks, since if this occurs the wipers will be damaged when the switch is jacked into position.

The general object of the invention is therefore to provide an improved vertical bank arrangement for use with a two-directional switch, this arrangement having the advantages that securing correct alignment of the wiper blades with the bank contacts is simplified, the banks of contacts are fixed, the bank wiring is simplified and rendered unable to interfere with the removal of adjacent switches, and further more the design is such that accidental damage to the wipers when jacking the switch into its mounting is prevented.

According to the invention, in an automatic switch of the vertical and rotary type, vertical contact banks are mounted on the main contact banks on both sides of the main wiper carriage, the corresponding wipers being mounted on the main wiper carriage so as to share its vertical but not its rotary movement.

In the case of vertical marking banks provided on switches of the vertical and rotary type, the distance between adjacent contacts is necessarily small owing to size limitations imposed on the bank, and it has therefore been found necessary hitherto to provide raised insulation between the bank contacts in order to avoid bridging of contacts during vertical movement of the switch, this arrangement having been particularly necessary to prevent bridging by wipers which have suffered considerable wear. The raised insulators between contacts have in turn resulted in wiper bounce and have tended to reduce the extent of contact of the wiper with the contacts to an amount less than the full width of the contact.

This difficulty may be simply overcome by the use of a wiper having a solid wire tip of substantially circular section the diameter of the wire being less than the space between the vertical bank contacts so that bridging can never occur no matter to what extent the engaging face of the tip wears down. As a result of this design it is possible to dispense with the raised insulation so that the wiper will operate on a level I track and will not bounce. The extent of contact of the wiper with each bank contact is immediately increased to the full width of the bank contact, and the practical advantage is obtained that a greater measure of wiper tip play can be tolerated without detriment to the operation of the switch.

The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the accompanying drawing comprising Figs. 1 and 2 which show an improved vertical bank and wiper applicable to a two-directional switch of the type disclosed in Saxby Patent No. 2,124,750, this switch being arranged to mount on a metal shelf member in the manner disclosed in SaXby Patent No. 2,067,246.

Fig. 1 shows a plan view of the vertical wiper and bank arrangement according to the invention, this view showing also in dotted section the two vertical frame members of the switch in order to indicate how the wipers maintain their position when the switch is removed from the shelf and so are protected against damage when the switch is subsequently jacked in position again. Fig. 2 is a front elevation of the vertical wiper and split bank assembly, part of the switch shaft being shown and also the main bank assembly in dotted outline.

It will be seen that the vertical bank is split into two single-sided 11-point assemblies 10 and H which are secured by screws I2 and l3, l4 and E5 to turned-over lugs I6 and H of a bracket i8 which is clamped between the main bank assembly i9 and the switch cradle mounting member Channel clamping plates 2i and 22 serve to clamp down the respective rows of contacts on to a block of insulating material which is moulded in such manner as to project upwards between each contact, the height of projection being preferably such that a level track is presented to the wipers so as to practically eliminate wiper bounce.

Considering now the construction of the wiper members and these are carried on an insulating block 25 which is supported on the switch shaft 28 between two collars '21 and 28 which are locked in position on the switch shaft, the arrangement being therefore such. that the wiper assembly shares the vertical movements of the shaft but is free to rotate thereon. The wipers themselves are of stirrup form and terte in solid wire tips which are of the shape ted in l and are preferably welded to the stirrup arms of the wipers.

As result of the arrangements described, it will be seen that all bank contacts and engaging wiper are readily visible for alignment purposes, the ertical banks being secured to the lugs of the mounting bracket :8 by the use of slotted holes so that up and down adjustment is readily possible. Since the banks are fixed, the wiring to the contacts may form part of the ordinary bank wiring multiple, so that a. iiinum of space is occupied by the wiring and le or no impediment is ofiered to the removal of the adjacent switches from the mounting rack.

"act that the wipers point in substantially cppo 1i ections enables the vertical frame member and 556 of the switch to form stops so as to prevent the wipers from turning through more than a small angle and thus possibly being by contact with the ordinary banks 'h is subsequently jacked into reference to the above-mentioned n0. 2,067,246, it will be seen that the e members are tapered at the bottom end a preferable to modify the tapered ends, either by direct modification in design or by the addition of small downwardly projecting strips which will "ialiy cover the tapered ends so that the wipers 1 be prevented from rotating when the switch is removed from the shelf.

In order to secure the contact strips firmly in position, they are preferably each provided with looking lips or projections which will engage with the moulded insulation material in such manner that it will not be possible to pull them out of no in these circumstances it will be position during wiring. The Contact strips are furthermore formed into a V or U shape in the part covered by the channel clamping plate so that any tendency for them to be twisted out of position during wiring is prevented.

To ensure that the clamping pressure is equally distributed over all the contacts, the contact strip at each end of the bank is formed at its centre part into a U shape so that it curves round the outer side of the relevant fixing screw of the channel clamping member. As a result, a solid foundation is provided for the ends of the clamping member which is thus assisted in remaining perfectly straight when the screws are tightened up and so maintains an even pressure on all contacts on the bank.

t will be understood that as shown the improved bank arrangement is applicable to switches of the construction considered provided with three or more banks without involving any modification thereto except as regards the addition of the vertical bank mounting plate 18 and the other necessary components. In the case of two-bank switches where the mounting space available for a vertical bank is rather severely limited, some modification will be required to the angular position of the locking lugs at the bottom ends of the channel side members of the switch and also to the corresponding locking bracket on the banks in order to provide the required mounting space.

I claim:

1. An automatic switch for use in telephone systems having a set of wipers with bank contacts accessible thereto and a shaft having vertical and rotary movement for moving the wipers to selected ones of said contacts, a frame-work supporting the shaft and contacts, a set of vertical bank contacts mounted on said framework on each side of the shaft, a pair of vertical wipers mounted on said shaft each engaging one of said sets of vertical bank contacts, said shaft having means for carrying said vertical wipers with it on its vertical movement but not on its rotary movement, and means on the framework for guiding said vertical wipers into position on the vertical banks when the switch is removed from and replaced on the frame-work.

2. An automatic step-by-step switch having the usual vertical and rotary wipers and an arcuate set of contacts accessible thereto with a frame-work supporting the contacts and also supportin a wiper shaft carrying the wipers, a set of vertical bank contacts mounted on each side of the shaft, a pair of vertical wipers moved with the shaft over said vertical contact on its vertical movement but slidable on the shaft when the same is rotated, said vertical wipers engaging their respective vertical banks on one side only to facilitate removal of the switch and wipers from the frame-work, each vertical wiper constituting the means for preventing rotary movement of the vertical wipers with the shaft in one direction.

EDGAR EUGENE COMFORT. 

